This invention relates to an improved countercurrent extraction process for accelerated decaffeination of coffee beans, and to the novel decaffeinated coffee product generated thereby. In particular, turbulent flow of the extracting solvent is used to obtain a substantially accelerated decaffeination rate involving a caffeine extraction time of only from about 3 to about 5 hours. Since the rate of extraction of non-caffeine coffee solubles is not correspondingly accelerated, the decrease in extraction time minimizes the loss of these valuable materials. Use of multiple vessels in countercurrent operation also decreases the loss of non-caffeine coffee solubles, resulting in an improved decaffeinated coffee.
A major problem in the commercial manufacture of decaffeinated coffee is the rather lengthy process times involved, resulting in higher costs for decaffeinated coffees than for non-decaffeinated coffee products. Decaffeination of green coffee beans typically involves five basic steps comprising steaming, pre-wetting, caffeine extracting, solvent stripping, and finally drying and cooling. These steps are well known and background information on them can be found in Sivetz, Coffee Processing Technology, Avil Publishing Co., Vol. 2, page 207-215 (1963); U.S. Pat. No. 897,840, issued to Meyer et al (1908); U.S. Pat. No. 936,392, issued to Wimmer (1909); U.S. Pat. No. 1,502,222 to Wimmer (1924); U.S. Pat. No. 1,957,358 to Scheele (1934); and U.S. Pat. No. 1,977,416 to Wilder (1934). Traditionally, these typical decaffeination processes could take a total time of about 31 to 43 hours, with about 24 to 36 hours of this total time required for the caffeine-extracting step.
Process improvements in recent years have decreased the caffeine extraction times to about 10 to 16 hours. U.S. Pat. No. 3,671,262 of Wolfson et al (1972) discloses that use of high solvent superficial velocities in combination with high solvent exchange rates reduces the caffeine extraction time to 16 hours. However, use of the increased solvent velocity rates alone and not in combination with increased exchange rates decreases the extraction time only to about 20 hours. U.S. Pat. No. 3,671,263 of Patel et al (1972) discloses that a combination of an increased pre-wetting bean moisture level with high solvent superficial velocities and high solvent exchange rates results in a decaffeination time of from 10 to 15 hours. The increase in prewetting moisture is related to a beneficial increase in flavor.
The process of the present invention differs from the traditional decaffeination process in several aspects. The steaming and prewetting steps are combined into one step. The higher bean pre-wetting moisture level of Patel et al is not employed because valuable coffee solubles are stripped from the beans by the water. The decaffeination rate is accelerated due to use of turbulent flow of the extracting solvent. The prior art processes claiming improved extraction times employed chlorinated hydrocarbon solvents. Chlorinated hydrocarbon solvents are not preferred for the present invention due to recent governmental concerns regarding their safety. Ethyl acetate, a nonchlorinated ester, is preferred as the solvent. Finally, solvent removal from the decaffeinated beans can be by means of the novel technique of differential pressure steam stripping comprising flash evaporation of the solvent during cyclic pressure variations.
The acclerated decaffeination process of the present invention decreases caffeine extraction time to about 3 to about 5 hours, a reduction by at least 50% in extraction time, while providing an improved coffee product through decreased loss of non-caffeine coffee solubles.
Accordingly, it is an object of this invention to provide an accelerated decaffeination process for green coffee beans.
Another object of this invention is to reduce the time required for caffeine extraction from coffee beans to about 3 to 5 hours through use of turbulent flow of the extracting solvent.
It is a further object of this invention to provide a novel, highly aromatic decaffeinated coffee.
These and other objects will become apparent from the following description and examples.